French authorities are enforcing “unprecedented restrictions on civil society” at the UN climate change talks in Paris, the author and activist Naomi Klein has said.

Klein said the ongoing talks were a victim of austerity as the French government had failed to provide adequate state funding, leading to heavy sponsorship by corporations. Meanwhile authorities have imposed a ban on mass protests around COP21, as the conference is known, in the wake of last month’s terror attacks in Paris.

“We have got unprecedented restrictions on civil society – they’ve handed a megaphone to the corporations and taken the megaphone away from the social movements,” Klein said. “It’s a combination of the role of corporations inside the COP and the banning of protests outside.

“We always knew that this was going to be the most corporate-sponsored COP, it’s a victim of austerity … You should at least be able to have a dialogue between the corporate solutions and the popular solutions, but only one side of the debate is being given a megaphone and the other side is being hauled out or banned.”

Activists have found creative ways around the ban on mass gatherings, with 10,000 pairs of shoes laid out where a climate march should have started and a human chain running past the Bataclan concert venue where 90 people died. But police have arrested protesters who they suspect will flout the ban, and hundreds of anti-capitalist protesters were kettled by police last Sunday.

Andrew Wilson, of the International Chamber of Commerce, said there had been “no real sense of isolation” for businesses inside the summit. “There is no sense that they are being given special treatment,” he said.

World leaders opened the conference on Monday (30 November) and negotiators are now trying to thrash out a new deal on limiting greenhouse gas emission post-2020 by the end of the week.

In May, it was announced that 20% of the £122m cost of the summit would be funded by companies including EDF, Air France, Renault-Nissan and Engie.

Klein spoke to the Guardian on Saturday (5 December) at Le Trianon theatre in Paris before a concert where Thom Yorke and Patti Smith played to “help raise consciousness” of the talks.